1. Field of the Invention
The present invention relates to an original scanning apparatus used with an electrophotographic copying machine, image reader and the like, and, more particularly, it relates to an original scanning apparatus which scans an original by driving a scanning unit.
2. Related Background Art
In the past, original scanning apparatuses of this kind, for example, an optical scanning apparatus as shown in FIG. 10 have already been known. This known optical scanning apparatus is intended to be used with an electrophotographic copying machine and the like, and includes a scanning unit 100 having an illumination lamp 102 for illuminating a surface of an original (not shown). The scanning unit 100 is slidably mounted, at its one end, on a guide rail 103 extending in a direction along which original is scanned, and is slidably abutted, at its the other end, against a guide member 104 extending in parallel with the guide rail 103. A mirror 101 incorporated into the scanning unit 100 acts to focus and expose an image recorded on the original onto a photosensitive member (not shown) through a focusing lens (not shown) and a mirror 105 which is moved at a speed of 1/2 of that of the scanning unit 100.
A driving means 107 positioned outside of the guide rail 103 operates to shift the scanning unit 100.
On the other hand, the scanning unit 100 has a free end portion only a lower end of which is fixed, and a supply cord 106 is connected, at its one end, to the free end portion of the scanning unit. The supply cord 106 extends from the other end thereof fixed to a frame (not shown) of the scanning apparatus toward a returning direction of the scanning unit 100 and is bent in a U-shape near the one end thereof to be connected to the scanning unit 100. Thus, the supply cord 106 can follow the movement of the scanning unit 100 while changing a position of the bent portion 106a thereof.
In such conventional scanning apparatus, since the driving means 107 including a driving wire 108, pulleys 109a, 109b and 109c, driving motor (not shown) and the like is arranged outside of the guide rail 103 and since electric parts such as a circuit board (not shown) and the like relating to power supply, as well as the supply cord 106, are arranged outside of the free end portion of the scanning unit, the scanning apparatus itself requires a space, along a lengthwise direction of the mirror 105, for installing the driving means 107, supply cord 106 and the like, thus arising a problem that the scanning apparatus cannot be made compact.
Further, in such a conventional scanning apparatus, when the scanning unit 100 reaches its scanning completion position (full scan position), the substantial portion or most part of the supply cord 106 which extends from the bent portion 106a to the above-mentioned other end must be supported by the scanning unit 100. Consequently, if the supply cord 106 has not a certain rigidity, it cannot maintain its proper posture, with the result that the supply cord will flex outwardly or downwardly to contact with the other element or elements of the scanning unit, thus distorting the image to be copied and/or damaging the supply cord 106 itself to threaten the security of the apparatus.
In order to eliminate the above-mentioned disadvantage, the supply cord is normally stiffened by applying a coating layer made of resin such as vinyl chloride or polyolefin onto a sheath of the supply cord 106.
However, in the supply cord coated by such resin layer, since the hardness of the coating resin layer is increased in response to the change in the circumferential condition (particularly, decrease in temperature), the supply cord 106 cannot be smoothly moved in the scanning operation of the scanning unit 100, with the result that the load derived from the slow-moving supply cord is applied to the scanning unit 100. Accordingly, in the case where the supply cord 106 is attached to the free end portion of the scanning unit 100, there arose a problem that, during the scanning operation, the free end portion of the scanning unit 100 was lifted due to the load from the supply cord 106, thus distorting the copied image considerably.